Automating running Debian in VirtualBox

I'm experimenting with service separation by having each service run in
its own operating system, all of the sharing hardware though. Why ?
Separation seems to be the only secure approach to running any software.
Check Joanna's blog out. I
went with VirtualBox on Debian 7 host, with, well, Debian 7 guests.
First I've prepared template VM by creating a new VM and just proceeding
with install. Then I tried spawning some clones of that, but having it
done manually takes quite some time and is error prone. Did somebody
say automation ? Yes ! First, clone a VM, regenerating MAC addresses and
making sure the resource caps are good:

The script above needs to be run on guest, I'm using scp with known ssh keys to upload it and
then run via ssh. This step is to be automated in the future. Points to
improve:

updating all the guests at once [Chef?]

monitoring all guests at once [Nagios?]

Summarizing, I'm now running a Tor node, file server, caldav, carddav
and some other services on my home server. All of them in separate VMs.
And it's running quite well with 2GB of RAM. For more info on my home
server build check its
hardware and basic
software.